1. Field of the Invention
The present invention pertains to the art of measuring and monitoring bioelectric signals using sensor systems incorporating at least one capacitive-type electric sensor and, more particularly, to an adjustable garment incorporating embedded psychological sensors.
2. Discussion of the Prior Art
It is widely known that electric potentials and fields are developed in free space from many different sources. For example, organs in the human body, including the heart and brain, produce electric fields throughout the body and in the space outside the body. For a variety of reasons, it is often desirable to measure these electric fields, such as in performing an electrocardiogram (ECG). Indeed, the measurement of bioelectric signals can provide critical information about the physiological status and health of an individual, and is widely used in monitoring, evaluating, diagnosing and caring for patients. Prior methods of measuring electric potentials associated with human or animal subjects employ securing gel-coated electrodes directly to the skin or scalp, or inserting electrodes into the body.
More specifically, electrodes that make a resistive (i.e. Ohmic) electrical contact have been predominantly employed in connection with measuring electric potentials produced by animals and human beings. The disadvantages of such resistive electrodes have been described previously and include discomfort for the patient, the requirement for conducting gels and/or adhesives, difficulty in establishing good electrical contact because of differing physical attributes of the subject (hair, skin properties, etc.), and the degradation in resistive coupling quality over time, among others. These limitations have created a significant barrier to the use of resistive electrodes over extended periods of time and/or when convenience of use is paramount.
Another type of sensor that has been proposed in measuring biopotentials is a capacitive sensor. Early capacitive sensors required a high mutual capacitance to the body, thereby requiring the sensor to also touch the skin of the patient. The electrodes associated with these types of sensors are strongly affected by lift-off from the skin, particularly since the capacitive sensors were not used with conducting gels. As a result, early capacitive sensors were not found to provide any meaningful benefits and were not generally adopted over resistive sensors. However, advances in electronic amplifiers and new circuit techniques have made possible a new class of capacitive sensor that can measure electrical potentials when coupling to a source on the order of 1 pF or less. This capability makes possible the measurement of bioelectric signals with electrodes that do not need a high capacitance to the subject, thereby enabling the electrodes to be used without being in intimate electrical and/or physical contact with the subject. Such capacitive-type sensors and sensing systems have been previously disclosed.
To enhance the measurement of bioelectric signals, there still exists a need for a system that can unobtrusively measure the signals with minimal set-up or preparation time. In addition, there exists a need for a bioelectric signal measuring system that is convenient to use, both for the patient and an operator, such as a nurse, doctor or technician. Furthermore, there exists a need for an effective bioelectric signal measuring system that is adaptable for use by many different sized patients. Specifically, a truly unobtrusive measurement system, which does not require significant preparation or modification for use by different patients, is needed.